1. Field of the Invention
The invention relates to a method for the manufacture of PuO.sub.2 -containing crystals by oxidation of plutonium in a nitric-acid starting solution to form Pu.sup.6+, precipitation of ammonium plutonyl carbonate-containing crystals through reaction with ammonium and carbonate ions, and subsequent separation and calcination of these crystals.
2. Description of the Prior Art
A method of this type is known from German Pat. No. 28 11 959, (U.S. Pat. No. 4,235,740). According to the patent, a nitric acid uranyl nitrate solution and a nitric acid plutonium nitrate solution are mixed. The plutonium in this solution mixture is oxidized to the valence stage 6 by heating and concentrating. Ammonium carbonate, ammonia and carbon dioxide are added in another vessel to the concentrated solution in dilute nitric acid. As a result of reaction with the ammonium carbonate ions there is produced ammonium uranyl plutonyl carbonate which is precipitated in crystal form. This ammonium uranyl plutonyl carbonate is filtered off, dried and calcined by heating it to about 600.degree. C. The calcined U/PuO.sub.2 product is in the form of mixed crystals which can be processed further into nuclear fuel for nuclear reactor fuel assemblies.